The applicant plans a series of solid phase enzyme immunoassay (EIA)/ ferritin-linked immunoassay (FLIA) kits for small peptides. Phase I will concentrate on leu-enkephalin as a model. The EIA/FLIA format may offer advantages of low cost, simplicity, shortened assay time and ambient assay temperatures. The applicant contends that any immunoassay is dependent on good antibody and that commercial enkephalin antibodies are plagued with high cross-reactivity between leu- and met-enkephalin. He will initiate a potential solution to this problem, using a molecular design approach to the immunogen. The ultimate goal is to provide a line of specific, sensitive, non-radioactive robust immunoassays for the major opioid peptides.